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Re: [Paparazzi-devel] Quadrotor with Lia 1.1 - a sudden loss control aut

From: Michal Podhradsky
Subject: Re: [Paparazzi-devel] Quadrotor with Lia 1.1 - a sudden loss control authori
Date: Mon, 12 Nov 2012 12:41:02 -0700

Hi Felix,

yes, so that is why I am surprised that the quad did not respond for the throttle commands from the RC pilot.
We are using Lia board from Quadshot ( with Aspirin IMU (actually we are using only the MS5611 barometer for pressure readings, not the gyros etc.) and GX3 IMU for attitude.

Unfortunately RC messages are not logged.
I checked the suggested logs:
1) 3-baro_abs-est_z.png shows the barometer absolute readings vs. estimated altitude. The baro is calibrated and performs better than BMP085
2) 4-frame_rate-motors_on-in_flight.png - Motors are on, we are in flight - so these are correct. The frame rate is scaled 1/10
3) 5-ap_mode-frame_rate.png - We can see that shortly after going from Z_HOLD to ATT the frame rate suddenly drops (from 45 to 10 fps), but AP didn't go to FAILSAFE, so I assume even 10 fps is enough, right? Or can this be the problem (Radio related)?


On Sat, Nov 10, 2012 at 7:28 AM, Felix Ruess <address@hidden> wrote:
Hi Michal,

this is very strange...
Whether you use the adaptive hover throttle or set a fixed NOMINAL_HOVER_THROTTLE makes no difference in the DIRECT vertical mode, it just takes the RC input and directly applies that to the thrust command:
So that should be fine..

From the plot, it doesn't look like the thrust command from the RC was put to 100%, which is very weird. 
I guess you didn't log the RADIO_CONTROL or RC messages in that flight?
Did you take a look at rc_status, frame_rate, ap_in_flight and ap_motors_on in the ROTORCRAFT_STATUS message? (Just to make really sure these are ok)

Could you please post your full config and flight logs?

Cheers, Felix

On Fri, Nov 9, 2012 at 10:30 PM, Michal Podhradsky <address@hidden> wrote:
Hi Loïc,

I am attaching the logs:
1) AP mode and Vertical mode vs. thrust command (scaled to fit). It is not obvious for the first sight, but after going from Z_HOLD(8) to ATT(3) our RC pilot was pulling throttle even up to 100% trying to keep the plane in the air, but it is not reflected in the plot until the last moment - right before the landing (t=239s)

2)  Vertical loop - est_z, est_zd, est_zdd and AP mode. You can see the quad was climbing rapidly during Z_HOLD, and then started to descend after switching to ATT.


On Fri, Nov 9, 2012 at 1:06 AM, Loic Drumettaz <address@hidden> wrote:

I never experienced such issue. I don't use adaptative estimator for thrust, but NOMINAL_THROTTLE instead (see Paparazzi vertical loops wiki page).  From my experience, it is sometime difficult to switch from RC_CLIMB mode to DIRECT mode for the pilot, because of the sudden change of throttle required to hover.
Maybe could you post your logs?


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Attachment: 3-baro_abs-est_z.png
Description: PNG image

Attachment: 4-frame_rate-motors_on-in_flight.png
Description: PNG image

Attachment: 5-ap_mode-frame_rate.png
Description: PNG image

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